I don’t know that you’ll get to 115psi, especially if some air “leaks” along the way. But in any event, always carry two!
Two?! What kind of advice is that?
To the OP: carry as many as possible. More is more. I keep a gross in my rack trunk.
I think he meant on his person on an actual ride…not in his car for the rest of the year 
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None, carry a pump. That way you’ll be able to get more than one flat;)
None. Carry a pump. What are you going to do if you have a defective CO2 or you still lose air? A hand pump has never let me down.
Are you talking about racing or training rides?
I carry two threaded 16g ones for racing and 4 12g non threaded for training. I also cary a small pump for longer races and training in case I have problems with the CO2 but I’ve never had to use the pump yet.
I carry 2 for training, and 1-2 for racing. For long trainig rides I also carry a small pump. But one cartridge should get the tire pumped up to 90-100psi, I dont konw about 115, but it’ll be enough to ride on.
I’ve had trouble topping my tube off to 120 psi with co2. Seems I also read that co2 is really just intended to get home. Is that right?
I raced today in Innsbrook, Missouri (Who Tris Harder) and had a flat at mile 4. My lone co2 cartridge blew up so I was screwed until someone helped me out 15 minutes into the ordeal. I will definitely race with a pump from now on. The few seconds it may cost me is well worth losing a whole race (and I missed 3rd in my age group by 6 seconds).
How fast can you get a tire to 120psi with a hand pump?
I recall having trouble even getting one to 100psi
Carry the same number of cartridges as spare inners.So one inner one cartridge. Supplement this with a pocket rocket pump (lightest ones are only 55g) just in case you get a slow puncture.
Don’t waste effort by carrying excess cartridges
Better still - don’t get a puncture in a race!
You missed 3rd in your AG after waiting 15 minutes for a pump?!
That’s amazing!
It was a beginner race. Thanks though. 